Cancer specific skin test materials of increased sensitivity, consisting of crude membranes from cultured tumor cells after infection with vesicular stomatitis virus, were prepared for testing in melanoma, lung and breast cancer patients. Additionally, soluble extracts of melanoma cells after infection with VSV were produced. Tumors routinely arose from BALB/3T3, C3H/10T 1/2, and freshly explanted adult connective tissue cells of mice if they were implanted subcutaneeously attached to 1x5x10mm plastic plates. Exposure of BALB/3T3 cells to phorbol esters, a tumor promoter, before implantation increased the number of tumors that appeared from 20% to 80% after two months. Cytogenetic evidence for over 10 to the eighth power chromosomal dosage variants in a tumor cell population, providing a basis for tumor progression through variation-selection, was obtained. Release of growth inhibition by cis-hydroxyproline correlated with neoplastic transformation. A frozen bank of human tumors that are transplantable in nude mice was implemented.